The thief had been operating in a jurisdiction which uses computer software that sends out alerts to businesses within a 30-mile radius. By the time the crook walked into the bank, tellers were already on the lookout for anyone with too many quarters.

Indeed, police and sheriffs departments from Florida to Washington State are discovering that ordinary citizens by the thousands seem eager to team with police in fighting crime - provided their partnership is geared around e-mails and Web pages.

"Over the last few years there's been a lot more use of citizens in police work," explains Jacqueline Helfgott, associate professor of criminal justice at Seattle University. "Police cannot do it all, so now the Internet can help citizens get involved with their community's police force."

Look, for example, at the small city of Fairmont, Minn. In late 2001, police created a "Fairmont's Most Wanted" list, posted it on their website, and called public attention to it through a newspaper article.

"When we first publicized it we had a real big response - and we apprehended four of those people in the first week," reports Sgt. Corey Klanderud, who handles technology issues for the department. In fact, during the list's first year, "ten or eleven" persons with warrants were arrested directly because of citizens who studied the website.

In one of those cases the department received an e-mail from a resident of Duluth, 300 miles north, who provided the address of a suspect that lived on the same street. "This technology is going to help us have more eyes and ears in the community," says the sergeant.

At the center of this crime-fighting evolution is a Minnesota firm, Citizen Observer. The company, whose software sent out an alert to the community that caught the burglar with the quarters in the Coke bottle, offers police agencies a four-part package to galvanize communities:

• The Business Alert Network, which permits police to contact participating businesses with warnings of scams, bad check artists, and profiles of burglaries.

• The Residential Crime Alert, where anyone can register to receive police bulletins, including suspect descriptions and photos.

• A School Alert Network that would communicate with parents in event of Columbine-like emergencies.

• Fugitives, Missing Persons & Unsolved Crimes - a virtual bulletin board posted with descriptions and photos, including a way for citizens to send police information.

"Before this, police response was much slower," explains Terry Halsch, president of Citizen Observer. "Most of the time the police would make a couple hundred photocopies of a poster, then someone would drive around and drop them on the porches of block-watch captains, and by that time the criminal could be two states away."

In business just three years, Citizen Observer contracts with about 130 police agencies in Minnesota, North Dakota, Wisconsin, Illinois, Michigan, Ohio, Arkansas, and Florida. About 50,000 businesses have signed on to receive crime alerts from departments using Citizen Observer services. Often, the service costs local police little or nothing, because a community business will routinely cover the costs in exchange for promotional considerations and links on Web pages.

"Our goal is to be nationwide with about 5,000 departments registered in the next three years - and millions of businesses," says Mr. Halsch.

Even without entrepreneurial crime-fighters, other police departments are discovering the Internet's promise. Michael Knapp, police chief for Medina, Wash., a wealthy bedroom community east of Seattle, had never heard of Citizen Observer. A couple of years ago, Chief Knapp acted on an idea from a resident to start up a Community E-Lert program which send e-mails to 1,200 subscribers.

Knapp likes his system's ability to target specific neighborhoods about specific problems. If bicycles are being stolen from Elm Street between 1st and 3rd Avenues, E-lerts go out to residents of the affected blocks.

"It changes policing because we involve the community in a partnership - in addressing the criminal problems of our city," Chief Knapp says. "When you do that you're going to become more efficient."

The E-lerts have also opened a dialogue that provides Medina's law enforcement officers with valuable insights into what citizens think of their police work.

Bill Berger, police chief of North Miami Beach, Fla., and a past president of the International Association of Chiefs of Police, believes the Internet itself fosters citizen involvement not seen before.

"A lot of times people don't want to get involved," he says. "But something about the anonymity of the internet makes citizen participation easier. They can e-mail information, say to us, 'Here - check this out.' It's almost like it creates a veil, an extra level of distance and safety."

Today, some 3,000 businesses and 10,000 residents use Citizen Observer's interface to actively ally with North Miami Beach police.

Chief Berger says his officers embrace the Internet in their work. "These guys would rather have their laptops than their weapons."